The specific goals of the investigators at the University of Minnesota include the following: a) the development and implementation of group wide studies; b) pilot new approaches for the diagnosis and treatment of childhood leukemia and solid tumors which can later be applied on a larger scale in group cooperative studies; c) evaluate new agents for the treatment of patients with refractory malignancies; d) extend the studies of bone marrow transplantation for the treatment of hematologic malignancies; e) evaluate the acute and chronic effects of therapy on vital organ systems; f) develop and implement new studies of the Intergroup Ewing's Sarcoma Study Committee.